nomadx38: As I said in my post, I would have thought tha the lamp diagnostic settings would have been enabled as a default on my car- but they appear not to be. I guess that I tend to put a lot of trust in the stuff that the VCDS cable says- perhaps too much trust!
I assume that your 2011 Polo is also a 6R model. When you say that "VCDS sometimes incorrectly identifies the status of a given byte", is there any pattern to when it shows the wrong display (i.e. when does it mis-report the settings) ?